The present invention concerns a procedure for photometric measurement of liquids in a reaction vessel by means of a radiation flow with a course perpendicular against a row of reaction vessels in an automatic analyser.
In procedures and devices known in the art, for instance, circular reaction vessels resembling test tubes are used, the measurement on the liquid in the reaction vessel being made from their side, perpendicularly to the vessel. The most serious drawback is then the fact that the measuring signal is altered by the circular shape of the tubular reaction vessel, whereby it is possible to obtain an exact reading only at the centre of the vessel. Therefore, mean values cannot be used at all, with the consequence that dirt particles and scratches easily cause errors in the results of measurements. In addition, the procedure is slow, and automation of the sample manipulation is difficult to arrange.
In another procedure known in the art, rows of reaction vessels (so-called cuvettes) are employed, which often have straight measuring surfaces. One makes in that case the measurement on one vessel at a time, directing the radiation flow through the liquid under measurement from one side of the reaction vessel. Dirt particles and scratches on the vessel still constitute a detriment and give rise to measuring errors. Moreover, the procedure is slow and automation of the sample movements is difficult because in the method two directions of movement must be provided for the cuvettes and these have to be synchronized with each other.